Day04 2021

2021-12-04 12:05:03 +01:00
parent 399d894c68
commit 97334d34eb
3 changed files with 684 additions and 0 deletions
@@ -0,0 +1,52 @@
+package be.vandewalleh.aoc.days
+
+import be.vandewalleh.aoc.utils.BaseDay
+import be.vandewalleh.aoc.utils.input.Day
+
+@Day
+class Day04 : BaseDay() {
+    private val parts by lazy { input.text.split("\n\n") }
+    private val numbers by lazy { parts[0].split(',').map { it.toInt() } }
+    private val boards by lazy {
+        parts.drop(1)
+            .map { it.lines().map { it.trim().split("\\s+".toRegex()).map { it.toInt() } } }
+    }
+
+    override fun part1() = boards
+        .map { playBoard(it, numbers) }
+        .minByOrNull { it.first }!!
+        .second
+
+    override fun part2() = boards
+        .map { playBoard(it, numbers) }
+        .maxByOrNull { it.first }!!
+        .second
+
+    private fun playBoard(board: List<List<Int>>, numbers: List<Int>): Pair<Int, Int> {
+        for (round in numbers.indices) {
+            val usedNumbers = numbers.take(round)
+            var winning = false
+            for (line in board) {
+                if (usedNumbers.containsAll(line)) {
+                    winning = true
+                    break
+                }
+            }
+            if (!winning) {
+                for (i in board[0].indices) {
+                    val column = board.map { it[i] }
+                    if (usedNumbers.containsAll(column)) {
+                        winning = true
+                        break
+                    }
+                }
+            }
+            if (winning) {
+                val unmarkedNumbers = board.flatten().toMutableSet().also { it.removeAll(usedNumbers) }
+                return round to unmarkedNumbers.sum() * usedNumbers.last()
+            }
+        }
+        error("No wins")
+    }
+
+}